The Global Oscillations Network Group [1]} project contains a network of six instruments for acquiring the low noise and long-term stable data. It is a community based mission for the vast study of the internal structure and dynamics of the Sun using helioseismology. GONG is operating and contributing to clarify the conditions in the solar interior with the knowledge of acoustic wave propagation through the Sun. The six different locations are chosen such that the long term observations from different sites will not disturbed by the daily setting of the Sun. These six observing networks are: Big Bear Solar Observatory (BBSO) in California USA, Mauna Loa Observatory in Hawai, USA, Learmonth Solar Observatory in Australia, Udaipur Solar Observatory (USO), India, Observatorio del Teide in Tenerife, Spain, and Cerro Tololo Interamerican Observatory, in Chile. The GONG project is very important and less costly as all the six networks are the ground based observatories. Space borne satellites are of course free from the terrestrial effects but expansive to implement and difficult to maintain. On the other hand ground based observatories can be repaired easily but the data contains terrestrial atmospheric disturbances.
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